Table 2. Association between aspirin taking and metastatic spread.

Author	Cancer	Numbers ASA/Control	Estimates of reduction (95% CI)
Restivo et al. [26]	Rectum	37/204	HR 0.31 (0.18, 0.54)
Shiao et al. [36]	Breast	65/157	HR 0.34 (0.15, 0.81)
Osborn et al. [38]	Prostate	147/142	HR 0.23 (0.06, 0.91)
Rosenberg et al. [48]	Colorectal	49/191	OR 0.96 (0.65, 1.40)
Sanbury et al. [49]	Colorectal	75/34	OR 0.77 (0.40, 1.48)
Leitzmann et al. [50]	Prostate	16/33,076	RR 0.71 (0.31, 1.62)
Pooled HR 0.31 (95% CI 0.18, 0.51) Heterogeneity P = 0.89; Egger’s test for bias 0.138